Dual pump system for automatic transmission augmentation, extended stop and start, and sailing

ABSTRACT

A dual pump system for a motor vehicle transmission includes a first pump connected to and co-rotated with a pump shaft rotated during operation of a motor vehicle engine. A second pump is connected to a motor shaft of an electric motor. A one-way roller clutch is connected to the second pump and to the pump shaft. The one-way roller clutch is configured to allow the faster rotated one of the pump shaft or the motor shaft to drive the second pump. The pump shaft and the motor shaft can be co-axially aligned or positioned off-axis with respect to each other.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 62/210,097, filed on Aug. 26, 2015, the entire contents of which are incorporated herein by reference.

FIELD

The present disclosure relates to an electric motor driven pump augmenting operation of a mechanically driven hydraulic pump for motor vehicle transmissions.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.

Many modern motor vehicle automatic transmissions, including continuously variable transmissions (CVT) utilize controlled hydraulic fluid (transmission oil) to actuate clutches. CVT transmissions also utilize hydraulic fluid to actuate the CVT belt and pulleys (or a chain and pulleys) to achieve a desired ratio to optimize fuel economy. The control of such hydraulic fluid is achieved by a valve body which comprises a plurality of spool valves which direct hydraulic fluid flow through a complex of passageways to transmission components including CVT pulley pistons as well as other clutch and brake actuators. The valve body is supplied with pressurized hydraulic fluid from, typically, a gear or vane pump, which is driven by the engine output shaft or the transmission input shaft.

Because this is such a common transmission configuration and because of the manufacturing volume of such automatic transmissions, extensive research and development has been undertaken to reduce the cost and optimize the performance of such pumps. For example, simplifying such pumps to reduce their weight and cost, reducing their size to improve packaging, improving low speed performance, improving low temperature performance, and reducing high speed energy losses have all been areas of development and improvement.

A fixed displacement pump normally driven by a shaft positioned off-axis from the transmission torque converter driven shaft provides flow proportional to engine speed. The pump sizing criteria is often driven by hydraulic pressure and volume demands of the transmission at engine low speed idle or during park-to-throttle shift conditions. Because friction forces inside the pump increase as the size of the surface area of the pump rotor increases, larger diameter, higher displacement pumps that meet hydraulic demands of the transmission near engine idle speed or during park-to-throttle shift conditions often contribute to undesirable transmission spin losses and decrease efficiency of the transmission when operated at vehicle steady speed driving conditions. A large pump will also provide much greater oil flow than what is consumed by the transmission at higher engine speeds, with higher pump power consumption leading to loss in overall transmission efficiency, and therefore a reduction in fuel economy.

The present disclosure is directed to a single axis dual pump design and improvements that reduce pump spin losses and improve transmission efficiency while augmenting hydraulic demands on a mechanical vane pump of an automatic transmission during engine idle speed and during park-to-throttle shift conditions.

SUMMARY

A dual pump system for a motor vehicle transmission includes a first pump connected to and co-rotated with a pump shaft rotated during operation of a motor vehicle engine. A second pump is connected to a motor shaft of an electric motor. A one-way roller clutch is connected to the second pump and to the pump shaft. The one-way roller clutch is configured to allow the faster rotating one of the pump shaft or the motor shaft to drive the second pump.

According to further aspects, the pump shaft and the motor shaft are co-axially aligned.

According to further aspects, the second pump is a gerotor gear pump.

According to further aspects, a housing of the gerotor gear pump is directly coupled to a pump housing of the first pump.

According to further aspects, the second pump is a vane pump.

According to further aspects, the second pump is a dual axis, dual gear pump.

According to further aspects, a longitudinal axis of the motor shaft of the dual axis pump is offset from a longitudinal axis of the pump shaft.

According to further aspects, the electric motor is a 12 volt DC brushless motor.

According to further aspects, the electric motor is a 48 volt DC brushless motor.

According to further aspects, the electric motor is a 300 volt DC brushless motor.

According to further aspects, the electric motor is an 80 watt motor.

According to further aspects, the electric motor is a 250 watt motor.

According to further aspects, the electric motor is energized when the pump shaft is not rotating, with the vehicle engine shut off, to provide hydraulic flow to the transmission.

According to further aspects, the electric motor is energized when the pump shaft is rotating, to rotate the motor shaft of the electric motor at a rotational speed faster than a rotational speed of the pump shaft to augment a hydraulic flow from the first pump with a hydraulic flow from the second pump.

Further features, advantages, and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the present disclosure. Moreover, in the figures, like reference numerals designate corresponding parts throughout the views. In the drawings:

FIG. 1 is a diagram showing a portion of a hydraulic control system implementing a dual pump system of the present disclosure;

FIG. 2 is an exploded assembly view of the dual pump system in accordance with the principles of the present disclosure;

FIG. 3 is a cross sectional front elevational view of the assembled dual pump system of FIG. 2;

FIG. 4 is an exploded assembly view of a dual gear pump of another aspect of the disclosure; and

FIG. 5 is a cross sectional front elevational view of an assembled dual pump system modified from the dual pump system defined in FIG. 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

With reference to FIG. 1, an exemplary powertrain for a motor vehicle is generally indicated by reference number 10. The powertrain 10 includes an engine 12 for providing power and torque to propel the motor vehicle. The engine 12 may be a conventional internal combustion engine or an electric motor, or any other type of prime mover, without departing from the scope of the present disclosure. An engine starter 13 is connected to the engine 12 to start the engine 12. The engine 12 is configured to provide driving torque to a starting device 14 through an engine output shaft 16. The engine output shaft 16 may be connected to the starting device 14 through a flexplate (not shown) or other connecting device. The starting device 14 may be a hydrodynamic device, such as a fluid coupling or torque converter, an electric motor, or a friction device such as a dry or wet launch clutch or dual clutch. It should be appreciated that any type of starting device 14 may be employed without departing from the scope of the present disclosure.

The transmission 20 may be a front wheel drive transmission or a rear wheel drive transmission. Generally speaking, the transmission 20 includes a transmission input shaft 22 and a transmission output shaft 24. The transmission input shaft 22 is functionally interconnected with the engine 12 via the starting device 14 and receives input torque or power from the engine 12. Accordingly, the transmission input shaft 22 may be a turbine shaft in the case where the starting device 14 is a hydrodynamic device, dual input shafts where the starting device 14 is dual clutch, or a drive shaft where the starting device 14 is an electric motor.

Disposed between the transmission input shaft 22 and the transmission output shaft 24 is a gear and clutch arrangement (not shown). The gear and clutch arrangement may include a plurality of gear sets, a plurality of clutches and/or brakes, and a plurality of shafts. The plurality of gear sets may include individual intermeshing gears, such as planetary gear sets, that are connected to or selectively connectable to the plurality of shafts through the selective actuation of the plurality of clutches and brakes. The plurality of shafts may include layshafts or countershafts, sleeve and center shafts, reverse or idle shafts, or combinations thereof. The clutches and brakes are selectively engageable to initiate at least one of a plurality of gear or speed ratios by selectively coupling individual gears within the plurality of gear sets to the plurality of shafts. It should be appreciated that the specific arrangement and number of the gear sets, clutches and brakes, and shafts within the transmission 20 may vary without departing from the scope of the present disclosure.

The transmission output shaft 24 is preferably connected with a final drive unit 26. The final drive unit 26 may include, for example, propshafts, differential assemblies, and drive axles. The transmission 20 also includes a transmission control module 28. The transmission control module 28 is preferably an electronic control device having a preprogrammed digital computer or processor, control logic, memory used to store data, and at least one I/O peripheral. The control logic includes a plurality of logic routines for monitoring, manipulating, and generating data. The transmission control module 28 controls the actuation of the transmission 20 via a hydraulic control system 30. The hydraulic control system 30 is operable to selectively engage the clutches and brakes by selectively communicating a hydraulic fluid to hydraulic actuators that mechanically engage the clutches and brakes. The hydraulic fluid is communicated to the clutches and brakes under pressure from a hydraulic pump system 32 connected to the hydraulic control system 30, as will be described in greater detail below.

The hydraulic pump system 32 is configured to provide pressurized hydraulic fluid to the hydraulic control system 30 and to provide power to the final drive unit 26 through the transmission 20. For example, in one embodiment of the present invention, the hydraulic pump system 32 defines an off-axis dual pump system 34. The dual pump system 34 is mechanically connected with a rotor or pump shaft 36. A first gear or sprocket 38 is connected to the pump shaft 36 while a second gear 40 is connected to the starting device 14, for example to a hub of an external housing of a torque converter forming a portion of the starting device 14, and driven at engine speed. A drive member such as a drive chain 42 rotationally couples the first gear or sprocket 38 with the second gear 40. The dual pump system 34 is in fluid communication with the hydraulic control system 30 via a first fluid port 44.

Referring to FIGS. 2 and 3, and again to FIG. 1, the dual pump system 34 embodying the principles of the present disclosure includes a first pump 46 which according to several aspects is a mechanically driven vane pump, which is axially aligned with a second pump 48 which can be either electrically or mechanically driven. According to several aspects, the first pump 46 can be a vane pump as described in U.S. Pat. No. 8,042,331 entitled “On-Demand Hydraulic Pump For A Transmission And Method Of Operation” which issued on Oct. 25, 2011, the contents of both of which are incorporated herein by reference in their entirety. The first pump 46 as a vane pump can be operated as a balanced vane pump with a balanced pressure output from its two flow ports, or can be operated as a binary pump with one of the two output flow ports isolated or closed. According to several aspects, the second pump 48 is a gerotor pump. The first and the second pumps 46, 48 are coupled to each other and coaxially mounted with respect to a pump shaft rotational axis 50. In some arrangements, the dual pump system 34 is an “off-axis pump” assembly completely submerged in a hydraulic fluid within a sump area of the automatic transmission 20 (only partially shown). The dual pump system 34 is herein defined as an “off axis pump” because the pump shaft rotational axis 50 of the driven pump shaft 36 is not co-axially aligned with the driving shaft or transmission input shaft 22 of the transmission 20.

Further details of off-axis pumps are described in U.S. Pat. No. 6,964,631 and U.S. patent application Ser. No. 13/475,559, filed on May 18, 2012 and entitled “Pump Assembly with Multiple Gear Ratios,” the contents of both of which are incorporated herein by reference in their entirety. Such arrangements employ, for example, an electric motor with a one way clutch to drive a rotor set of a pump, whether the pump is a balanced vane pump or a Gerotor gear pump. The first pump 46 and the second pump 48 together define a coupled binary pump which can communicate with the transmission hydraulic control system 30 similar to the controlled operation of the binary pump described in U.S. patent application Ser. No. 14/247,867, filed on Apr. 8, 2014, and entitled “Binary Pump For A Transmission”, the contents of which are incorporated herein by reference in their entirety.

The dual pump system 34 is in part mechanically driven by the chain 42 that engages with the driven sprocket 38 attached to a splined end 52 of the pump shaft 36 thereby acting to axially rotate the pump shaft 36 at a rotational speed of the engine 12 of the vehicle. The pump shaft 36 extends through a structural front support 54 of a housing of the transmission 20. The pump shaft 36 can be sealed at the structural front support 54 using a face seal 56. A torsional or sprocket load applied at the driven sprocket 38 of the pump shaft 36 is carried by a bearing assembly 58 to mitigate against the driven sprocket torsional load deflecting or being imparted to the pump shaft 36.

According to several aspects, the first pump 46 includes a pump housing 60 having a vane or rotor 62 disposed on the pump shaft 36 and rotated by the pump shaft 36 within the pump housing 60. The rotor 62 is received in a cam 64 having the pump shaft 36 extending centrally therethrough. A port or thrust plate 66 is fastened to the pump housing 60 which retains the rotor 62 and the cam 64 within a cavity of the pump housing 60. The thrust plate 66 can either be directly fastened to the structural front support 54, or in further aspects, a seal plate 68 can be positioned between the thrust plate 66 and the structural front support 54. When used, the seal plate 68 can include hydraulic fluid ports for inlet and discharge porting. A fluid filter 70 can be connected to a pump inlet 72 of the pump housing 60, which functions to filter hydraulic fluid prior to entry into the pump housing 60. According to several aspects, a fluid connection (not shown) can also be made between the filter 70 and an inlet of the second pump 48 to filter the hydraulic fluid prior to entry into the second pump 48.

The second pump 48 includes an electric motor 74, which according to several aspects is a 12 Volt DC brushless motor. According to other aspects the electric motor 74 can also be a 48 Volt DC brushless motor, or a 300 volt DC brushless motor. According to several aspects, the electric motor 74 is an 80 watt motor. According to other aspects, the electric motor 74 is a 250 watt motor. The power rating of the electric motor 74 can be increased to the 250 watt rating for example to increase the operating pressure of the second pump 48 or to improve a low temperature operating point of the system. A motor controller 76 is connected to the electric motor 74 which receives commands for operation of the electric motor 74 from the transmission control module 28. According to several aspects the second pump 48 is a gerotor pump 78 which includes a gerotor inner gear 80 disposed within a gerotor outer gear 82. The gerotor pump 78 is received in a cavity 83 of a cover or gerotor housing 84 which is connected for example using fasteners to a housing of the electric motor 74.

Fasteners 86 are used to connect an assembly of the electric motor 74, the motor controller 76, and the gerotor housing 84 directly to the pump housing 60 such that the gerotor housing 84 is directly connected to the pump housing 60 and to the structural support 54. The pump housing 60 includes a bore 88 co-axially aligned with the longitudinal axis 50 of the pump shaft 36 such that a portion of the pump shaft 36 extends through the bore 88 into the gerotor housing 84. A one-way roller clutch 90 is rotatably coupled with the pump shaft 36, and is fixed to the gerotor inner gear 80. The one-way roller clutch 90 can be provided for example as an HFL series drawn cup roller clutch manufactured by the Schaeffler AG Corporation, of Herzogenaurach, Germany, as well as from other sources. The one-way roller clutch 90 therefore rotatably couples a motor shaft of the electric motor 74 to the pump shaft 36, which will be shown and described in greater detail in reference to FIG. 3.

With continuing reference to FIG. 3 and referring again to FIGS. 1 and 2, according to several aspects, the dual pump system 34 when assembled and installed includes the pump housing 60 fastened to the structural front support 54 with the seal plate 68 positioned between the pump housing 60 and the structural front support 54. The pump housing 60 provides opposed pressure plates including a first pressure plate 92 having a first face providing an exemplary 20 microns of end clearance with hydraulic fluid oil film to allow rotation of the rotor 62, and also a second face contacting the seal plate 68. A second pressure plate 94 of the pump housing 60 includes a first face providing an exemplary 20 microns of end clearance for hydraulic fluid oil film to allow rotation of the rotor 62 and a second face providing an attachment surface directly contacting the gerotor housing 84. According to several aspects, the first and second pressure plates 92, 94 of the pump housing 60 can be rigid, or can allow elastic deflection to provide axial pressure compensation for the rotor 62 at high discharge pressure. Axial pressure compensation provides for the first and second pressure plates 92, 94 to each be designed to elastically deflect under pressure loading from the pressurized hydraulic fluid. The value of this deflection is predetermined to reduce “end clearances” between approximately 10 microns to approximately 30 microns between either of the first or second pressure plates 92, 94 and the rotor 62, to limit pump internal clearance at high pressure to improve pump volumetric efficiency.

At the location where the pump shaft 36 penetrates the second pressure plate 94 via the bore 88, a bushing 96 rotatably supports the pump shaft 36, but allows some leakage of hydraulic fluid for rotational lubrication of the pump shaft 36. An engagement end 98 of the pump shaft 36 extending outward of the pump housing 60 is received in a coupling bore 100 of the one-way roller clutch 90. The one-way roller clutch 90 is externally coupled to the gerotor inner gear 80 such that rotation of the one-way roller clutch 90 by axial rotation of the pump shaft 36 co-rotates the gerotor inner gear 80 when either the electric motor 74 is de-energized, or if a rotational speed of the pump shaft 36 exceeds a rotational speed of the electric motor 74.

The electric motor 74 when energized axially rotates a motor shaft 102, which according to several aspects is coaxially aligned with the longitudinal axis 50 of the pump shaft 36. The motor shaft 102 is rotatably supported at opposite ends using first and second bearing assemblies 104, 106. A permanent magnet rotor 108 carried by the motor shaft 102 is induced to rotate the motor shaft 102 by excitation of a stator 110 using signals from the controller 76. A splined end 112 of the motor shaft 102 engages a similarly splined bore 114 of the gerotor inner gear 80 and thereby rotates the gerotor inner gear 80 when the electric motor 74 is energized.

The one-way roller clutch 90 allows the gerotor pump 78 to rotate at the operational speed of whichever of the pump shaft 36 or the motor shaft 102 is rotating faster. For example, if the electric motor 74 is de-energized when the pump shaft 36 is rotating, the pump shaft 36 rotates the first pump 46, and also through engagement of the one-way roller clutch 90 co-rotates the gears of the gerotor pump 78, thereby mechanically co-rotating both the first pump 46 and the second pump 48 at the same speed of rotation as the pump shaft 36. When the electric motor 74 is energized, if the rotational speed of the motor shaft 102 is below that of the rotational speed of the pump shaft 36, the one-way roller clutch 90 couples the gerotor pump 78 to the pump shaft 36, allowing the speed of rotation of the pump shaft 36 to control the speed of rotation of the gerotor pump 78. When the electric motor 74 is energized, and when the rotational speed of the motor shaft 102 exceeds the rotational speed of the pump shaft 36, the one-way roller clutch 90 decouples the gerotor pump 78 from the pump shaft 36, allowing the higher speed of rotation of the motor shaft 102 to control the speed of rotation of the gerotor pump 78, which thereby exceeds the speed of rotation of the pump shaft 36. Concomitantly, if the electric motor 74 is energized when the vehicle engine is off and therefore when the pump shaft 36 is not rotating, for example during an engine start-stop operation, the motor shaft 102 and the gerotor pump 78 will rotate at the speed set by the controller 76 without impacting the non-rotating pump shaft 36.

The one-way roller clutch 90 therefore allows the electric motor 74 to be de-energized during engine operation with the pump shaft 36 rotating while still providing mechanical rotation of both the first pump 46 and the second pump 48. It is acceptable to permit the motor shaft 102 to continue to rotate when the electric motor 74 is off, because electric motor shaft 102 parasitic or drag losses are low, for example less than approximately 0.05 Nm. Additionally, the one-way roller clutch 90 also allows the electric motor 74 to be energized during engine operation with the pump shaft 36 rotating to permit the second pump 48 to be operated at either the same rotational speed as the pump shaft 36, or at a higher operating speed than the pump shaft if the electric motor 74 is operated at a higher speed than the pump shaft 36. Still further, the electric motor 74 can be energized to rotate the second pump 48 while the pump shaft 36 and therefore the first pump 46 are not rotating.

The above characteristics of the dual pump system 34 permit the second pump 48 to be independently operated to augment the hydraulic flow and pressure delivered by the first pump 46. The dual pump system 34 therefore allows the first pump 46 to be sized at the lower system hydraulic demand of steady state highway driving conditions, which coincides with vehicle optimum fuel economy. The electric motor 74 can also be operated at a selected higher rotational speed than the rotational speed of the pump shaft 36, thereby rotating the second pump 48 at a higher rotational speed than the pump shaft 36 rotates the first pump 46, augmenting hydraulic flow of the first pump 46 with a selectable hydraulic flow of the second pump 48 to the transmission clutches.

The terms “augment” or “augmentation” as used herein are defined as the ability to provide a variable capacity hydraulic fluid flow through operation of the second pump 48, by increasing the speed of operation of the electric motor 74 such that the rotational speed of the second pump 48 is increased above the rotational speed of the pump shaft 36. This increases the rotational speed of the motor shaft 102 above the engine speed, such that the second pump 48 provides an additional component of hydraulic flow greater than the combined flow provided by the first and second pumps 12, 14 when the first and second pumps 46, 48 are limited to operation at the rotating speed of the pump shaft 36. This permits the first pump 46 to be sized for the smaller hydraulic system flow required for steady state driving operation, with the speed of the second pump 48 increased when needed to augment or temporarily increase hydraulic flow to provide the balance of hydraulic system flow required for non-steady state driving conditions.

During operation of a motor vehicle having the dual pump system 34 of the present disclosure, components of the dual pump system 34 can be operated as follows. With the vehicle operating at a steady highway speed hydraulic flow requirements are minimal, therefore the electric motor 74 can be de-energized and the system hydraulic requirements can be met by operation of the first and second pumps 12, 14 which are co-driven using the one-way roller clutch 90 at the rotational speed of the pump shaft 36. If an up-shift or a down-shift is requested, the electric motor 74 can be temporarily energized, and set to operate at a higher rotational speed than the pump shaft 36, thereby rotating the second pump 48 at a higher speed than the first pump 46 to temporarily augment the flow of the first pump 46 to thereby provide the additional hydraulic flow needed to fill clutches of the transmission 20. This temporary operation of the electric motor 74 can be initiated in approximately 100 milliseconds from a sensed shift request. The electric motor 74 can thereafter be operated for approximately 1 to 3 seconds to perform the shift, which commonly occur in approximately 1 second, and then de-energized. If a start-stop operation occurs during which the vehicle stops, for example at a traffic light, the engine 12 can be shut down, stopping rotation of the pump shaft 36. During a start-stop operation, the electric motor 74 is energized to deliver hydraulic flow and pressure necessary to maintain clutch readiness for engine re-start and an up-shift or down-shift of the transmission 20.

The dual pump system 34 also advantageously provides for operation of the vehicle during an “extended start-stop” operation and for a “sailing” operation. An extended start-stop is defined as a vehicle deceleration during which the transmission clutches may still be holding torque because the vehicle is still decelerating toward a stop, where it is anticipated that a stop event will occur, and it is therefore desirable to stop the engine and rotation of the pump shaft 36 to improve fuel economy. During the extended start-stop operation, the engine will be shut off, the pump shaft 36 will stop rotating, and the first pump 46 will not be rotating, therefore the electric motor 74 is energized to operate the second pump 48 to deliver hydraulic flow necessary to maintain transmission clutch conditions.

“Sailing” is defined as operation of the vehicle for an extended period of time, for example approximately 10 to 20 seconds, during which the vehicle is moving, but it is advantageous to shut down the engine to improve fuel economy. This may occur for example during downhill travel when engine power is not required to maintain vehicle speed, and therefore when it is desirable to shut down the engine to conserve fuel and to prevent engine windmilling. The electric motor 74 is also energized during the “sailing” operation to operate the second pump 48, thereby delivering hydraulic flow necessary to maintain transmission clutch readiness for engine re-start and an up-shift or a down-shift of the transmission 20 when the operator depresses the accelerator pedal.

Although the duty cycle of the electric motor 74 is affected, operation of the electric motor 74 for the extended periods of the “extended start-stop” and for the “sailing” operations will not thermally degrade the system components. This is due to the components of the dual pump system 34, including the electric motor 74, being entirely submerged in hydraulic fluid in a sump of the transmission 20, thereby providing convective and inductive cooling of the electric motor 74 by the controlled temperature (approximately 90 degrees Centigrade) of the transmission hydraulic fluid.

The augmentation provided by the second pump 48 and the electric motor 74 offer several benefits. Because the electric motor 74 can be operated during system conditions requiring additional hydraulic flow, such as during a garage shift, a down-shift, or an up-shift, the first pump 46 can be down-sized to more closely provide the hydraulic requirements of the system at steady highway operational speed. This eliminates the operational losses that would occur if the first pump 46 is “oversized” and therefore provides more flow than required, and operates with a higher parasitic friction loss during steady highway operational speed. The electric motor 74 and the second pump 48 can also be operated at a greater rotational speed than the rotational speed of the pump shaft 36, which is permitted by the use of the one-way roller clutch 90, allowing the rotational speed of the second pump 48 to exceed the rotational speed of the engine.

It is noted that with a traditional single rotor binary balanced vane pump, the pump delivers high pressure hydraulic fluid at either 100% or 50% of flow (referred to as a 50/50 split) since both discharge ports have the same projected area against the pump shaft. The arrangement shown in FIGS. 2 and 3 enables more optimized flow delivery including a modified flow delivery split, such as, for example, 80/20 percent of flow delivery to minimize pump power consumption while providing optimal flow delivery to the transmission. In certain transmissions, however, such as continuously variable transmissions, the transmission employs both high pressure and low pressure hydraulic fluid. Accordingly, the arrangement of the first pump 46 and the second pump 48 enables the delivery of both high pressure hydraulic fluid and low pressure hydraulic fluid to best optimize pump power consumption. Driving both pumps can be advantageous at lower ambient temperature when higher fluid viscosity could cause torque to exceed what may be produced by the motor, enabling use of a smaller power motor.

In some aspects, the dual pump system 34 employs the first pump 46 for providing both low pressure hydraulic pump requirements and for high pressure hydraulic pump requirements, and employs the second pump 48 provided as a Gerotor gear pump to supply low pressure hydraulic fluid for cooling and lubrication requirements of the transmission 20. This can be accomplished by use of separate pressure regulator valves (not shown) hydraulically connected to each of the first pump 46 and the second pump 48. For example, the first pump 46 can be operated at a very high pressure, such as, for example 60 BAR, while the second pump 48 can be operated at a low pressure, such as, for example, 7 to 12 BAR for use in a continuously variable transmission.

According to several aspects, a dual pump system 34 includes a first pump 46 connected to and co-rotated with a pump shaft 36 rotated during operation of a motor vehicle engine 12. A second pump 48 is connected to a motor shaft 102 of an electric motor 74. A one-way roller clutch 90 is connected to the second pump 48 and to the pump shaft 36. The one-way roller clutch 90 is configured to allow the faster rotating one of the pump shaft 36 or the motor shaft 102 to drive the second pump 48. The pump shaft 36 and the motor shaft 102 are co-axially aligned.

In some aspects, the first pump 46 and the second pump 48 are both enclosed in a generally cylindrical housing (not shown) that can be formed of two or more parts.

Referring now to FIG. 4 and with continuing reference to FIGS. 1 through 3, according to several aspects the dual pump system 34 can be modified to replace the second pump 48 with a double gear pump 116 in lieu of the gerotor pump 78. Double gear pump 116 is commonly referred to as an external-external, or X-X pump. In the pump 116, a first gear 118 is coupled to the one-way roller clutch 90, and a second gear 120 is coupled to a motor shaft 122 of an electric motor 124. The pump 116 can have a smaller volumetric displacement than the displacement of the gerotor pump 78, for example approximately 0.5 to 1.5 cc per revolution compared to approximately 1.5 to 5.0 cc per revolution for the gerotor pump 78, while having a higher mechanical efficiency than the gerotor pump 78. The two gear configuration of pump 116 also permits a longitudinal and rotational axis 126 the motor shaft 122 of the electric motor 124 to be offset from the longitudinal axis 50 of the pump shaft 36. This provides additional arrangement flexibility within the transmission 20 for positioning of the electric motor 124 compared to the in-line space envelope of the dual pump system 34. The dual gear design of pump 116 provides the additional benefit that it can also augment to a higher system pressure than the gerotor pump 78 due to the smaller displacement.

The pump 116 further includes a first port plate 128 and a second port plate 130 individually positioned on opposite sides of the first and second gears 118, 120. The first and second port plates 128, 130 together with the first and second gears 118, 120, are received in a shape-conforming cavity 132 of a pump housing 134. Similar to the gerotor pump housing 84, the pump housing 134 is also adapted to be directly mounted to the pump housing 60 of the first pump 46. A controller 136 for the electric motor 124 is also connected to the transmission control module 28 and therefore functions similarly to controller 76 to direct when pump 116 is energized as well as to control an operational speed of the electric motor 124.

Referring now to FIG. 5 and with continuing reference to FIG. 2, a dual pump system 138 embodying the principles of the present disclosure includes a first pump 140 which according to several aspects is a mechanically driven vane pump, which is axially aligned with a second pump 142 which is an electrically driven gerotor pump. According to several aspects, the first pump 140 can include a vane pump unit 144 axially rotatable with respect to the longitudinal axis of a shaft 146. The shaft 146 is rotatably connected to a motor shaft 148 using a one-way roller clutch 150, which functions similar to the one-way roller clutch 90 described in reference to FIGS. 2 and 3. The motor shaft 148 extends through a pump cover 152 and is rotatably supported to the pump cover 152 by a bush 154. The pump cover 152 separates the first pump 140 from the second pump 142.

The second pump 142 includes a gerotor pump assembly 152 including a gerotor pump inner gear 158 connected to the motor shaft 148 by a spline 160, and a gerotor pump outer gear 162 engaged to the gerotor pump inner gear 158. The gerotor pump assembly 152 is rotatably supported in a pump body 164, which is sealed at the motor shaft 148 by a bush 166. A motor rotor 168 is connected to a free end of the motor shaft 148 by a spline 170. A motor stator 172 surrounds the motor rotor 168 and is separated from the motor rotor 168 by an air gap 174. The motor rotor 168, the motor stator 172 and the gerotor pump assembly 152 are all contained within a single motor housing 176. A motor controller 178 is connected to the motor housing 176 and the electric motor defined by the motor rotor 168 and the motor stator 172 receives commands for operation from the transmission control module 28 defined in reference to FIG. 1.

The one-way roller clutch 150 allows the gerotor pump assembly 152 to be co-rotated together with the vane pump 144, or when the motor stator 172 is energized, the motor rotor 168 and thereby the gerotor pump assembly 152 can be independently operated. According to several aspects, the gerotor pump assembly 152 extends into an internal space envelope defined by the motor rotor 168 and the motor stator 172. The motor rotor 168 and the motor stator 172 therefore at least partially surround the gerotor pump assembly 152 to minimize an axial length of the second pump 142, and therefore to minimize an axial length of the dual pump system 138 compared to the dual pump system 34 shown and described in reference to FIG. 2.

According to further aspects, the one-way roller clutch 90 can be omitted and the second pump can be directly connected to the first pump, for example by sharing a same pump housing or having the second pump fastened to the first pump. The two pumps can share inlet porting, with the second pump defining an electric motor driven pump and therefore not mechanically connected to the mechanical driven shaft of the first pump.

The description of the present disclosure is merely exemplary in nature and variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A dual pump system of a transmission, comprising: a first pump connected to and co-rotated with a pump shaft rotated during operation of a motor vehicle engine; a second pump connected to a motor shaft of an electric motor; and a one-way roller clutch connected to the second pump and to the pump shaft; wherein the one-way roller clutch is configured to allow the faster rotating one of the pump shaft or the motor shaft to drive the second pump.
 2. The dual pump system of claim 1, wherein the pump shaft and the motor shaft are co-axially aligned.
 3. The dual pump system of claim 1, wherein the second pump is a gerotor gear pump.
 4. The dual pump system of claim 3, further including a housing of the gerotor gear pump directly coupled to a pump housing of the first pump.
 5. The dual pump system of claim 1, wherein the second pump is a vane pump.
 6. The dual pump system of claim 1, wherein the second pump is a dual axis, dual gear pump.
 7. The dual pump system of claim 6, wherein a longitudinal axis of the motor shaft of the dual axis pump is offset from a longitudinal axis of the pump shaft.
 8. The dual pump system of claim 1, wherein the electric motor is a 12 volt DC brushless motor.
 9. The dual pump system of claim 1, wherein the electric motor is a 48 volt DC brushless motor.
 10. The dual pump system of claim 1, wherein the electric motor is a 300 volt DC brushless motor.
 11. The dual pump system of claim 1, wherein the electric motor is an 80 watt motor.
 12. The dual pump system of claim 1, wherein the electric motor is a 250 watt motor.
 13. The dual pump system of claim 1, wherein the one-way roller clutch permits the electric motor to be energized to rotate the motor shaft independently of the pump shaft when the pump shaft is not rotating and with the vehicle engine shut off, to provide hydraulic flow to a transmission.
 14. The dual pump system of claim 1, wherein when the electric motor is energized when the pump shaft is rotating thereby rotates the motor shaft of the electric motor at a rotational speed faster than a rotational speed of the pump shaft to augment a hydraulic flow from the first pump with a hydraulic flow from the second pump.
 15. A dual pump system of a transmission, comprising: a first pump defining a vane pump connected to and co-rotated with a pump shaft rotated during operation of a motor vehicle engine; a second pump connected to a motor shaft of an electric motor; and a one-way roller clutch connecting the motor shaft to the pump shaft; and a bushing rotatably supporting the motor shaft to a housing, the housing positioned between and separating the first pump from the second pump.
 16. The dual pump system of claim 15, wherein the electric motor includes a motor rotor and a motor stator, the motor rotor, the motor stator and the second pump all contained within a single motor housing.
 17. The dual pump system of claim 16, wherein: the second pump defines a gerotor pump assembly; the pump shaft and the motor shaft are co-axially aligned; and the motor rotor and the motor stator at least partially surround the gerotor pump assembly.
 18. The dual pump system of claim 15, wherein when the electric motor is energized when the pump shaft is rotating, the motor shaft of the electric motor is rotated at a rotational speed faster than a rotational speed of the pump shaft to augment a hydraulic flow from the first pump with a hydraulic flow from the second pump.
 19. The dual pump system of claim 15, wherein when the electric motor is de-energized when the pump shaft is rotating, the pump shaft rotates the first pump, and also through engagement of the one-way roller clutch with the motor shaft co-rotates the second pump, thereby mechanically co-rotating both the first pump and the second pump at the same speed of rotation as the pump shaft.
 20. A dual pump system of a transmission, comprising: a first pump connected to and co-rotated with a pump shaft rotated during operation of a motor vehicle engine; a second pump connected to a motor shaft of an electric motor; and a one-way roller clutch connected to the second pump and to the pump shaft; the one-way roller clutch configured such that: when the electric motor is de-energized and the pump shaft is rotating the one-way roller clutch co-rotates the motor shaft; when the electric motor is energized and the pump shaft is rotating, the motor shaft of the electric motor rotates at a rotational speed faster than a rotational speed of the pump shaft to augment a hydraulic flow from the first pump with a hydraulic flow from the second pump; and when the electric motor is energized and the pump shaft is not rotating, the motor shaft is rotated such that the second pump provides a hydraulic flow with no hydraulic flow generated from the first pump. 